Strait Pipe or not to Strait Pipe???

warp2diesel · **Posted:** Sat Sep 13, 2008 10:35 pm

Here is Boyle's Law: http://en.wikipedia.org/wiki/Boyle%27s_law

Interesting fact among the Dynamometer crowd, the pressure from the boost of the turbo is enough that if you could remove the rod caps with the engine moving, the rods would keep riding on the crank journals.
Many stock Gassers need back pressure to reduce the strain on the rod cap bolts. Our CRDs don't need back pressure, free flowing exhaust is best

CRDMiller · **Posted:** Sat Sep 13, 2008 10:39 pm

I had a turn down at the flange with a gutted part trap and I loved it, except for the 40-50 hertz 200db tone at light throttle on flat or particularly on a incline @ around 1600 rpm's

And i know others here use straight piping while de-clawed and say it's similar in noise to stock, so i ask, is there a diffrence in noise between open flange/turn down and actual straight piping?

On the flats it's fine but under a decent load it's enough to make my ears ring.

fastRob · **Posted:** Sat Sep 13, 2008 11:04 pm

CRDMiller wrote:

I had a turn down at the flange with a gutted part trap and I loved it, except for the 40-50 hertz 200db tone at light throttle on flat or particularly on a incline @ around 1600 rpm's

And i know others here use straight piping while de-clawed and say it's similar in noise to stock, so i ask, is there a diffrence in noise between open flange/turn down and actual straight piping?

On the flats it's fine but under a decent load it's enough to make my ears ring.

As a 3" Cat backer I went with the 3" Magnaflow to tame what I expect to be nasty notes at certain rpm's.
Never tried it with out the Magnaflow.
My next step is to expand the top of the exhaust manifold to get as much flow as I can get the whole way through.
Any ideas?

Who is off topic?
Love the picture of the dawg flat out.

2mopar_diesels · **Posted:** Sat Sep 13, 2008 11:32 pm

I just asked simply about how a strait pipe sounds in the CRD Liberty and it went into the area of throttle/air intake & turbo restriction/fueling etc. all good info, just not what I was looking for. Thats all. I'm not at all new to diesel tech, just new to the Liberty CRD.

warp2diesel · **Posted:** Sat Sep 13, 2008 11:32 pm

When you study fluid dynamics there are factors that determine weather the flow is laminar flow or turbulent flow. With the snail shell of the turbo housing and the vanes of the turbine wheel the flow through the turbo is laminar. As soon as it exits just past the outlet it becomes turbulent flow and requires a larger pipe to carry the same volume of exhaust. Another factor to consider is that as the exhaust travels it cools down and reduces in volume. The perfect exhaust would be a tapered extractor that blends into a larger pipe, but having it go through the cabin on the passenger side would not be practical.
If you change the exhaust side of the turbo you will lose boost pressure and mess things up.
To design the ultimate exhaust system with out a lot of trial and error would require a dyno in a wind tunnel, lots of pressure taps and EGT probes in the the exhaust system to find the bottle necks causing restriction.

2mopar_diesels · **Posted:** Sat Sep 13, 2008 11:32 pm

I just asked simply about how a strait pipe sounds in the CRD Liberty and it went into the area of throttle/air intake & turbo restriction/fueling etc. all good info, just not what I was looking for. Thats all. I'm not at all new to diesel tech, just new to the Liberty CRD.

Inc · **Posted:** Sat Sep 13, 2008 11:50 pm

Stay on topic or this thread wil get locked regardless of what you think is on or off topic. The OP posted this question:

"if the ol' Dodge diesel sounds good with a strait pipe", just what would the Libby sound like without a muffler but leaving the cat???"

Feel more than free to answer this question or else things will be deleted and or locked. If you want to discuss and debate diesel throttle, start a new thread and keep it civil but no one here asked for a pissing match about it.

nursecosmo · **Posted:** Sun Sep 14, 2008 10:27 am

A couple of years ago I got the bright idea into my head to straight pipe my 6.9 ford F250. When I bought it it already had Twice pipes So I thought that it couldn't be much louder than it already was. Boy was I surprised at how LOUD it was :shock:

. After that my dog wouldn't ride with me anymore. Now, I like loud pipes but I would not recommend that particular operation to anybody. It is surprising how much the turbo can quiet things down compared to a NA diesel engine.

flash7210 · **Posted:** Mon Sep 15, 2008 2:35 pm

Go ahead and cut out that muffler. :twisted:

I did and I love it.
Mine dumps out the side, right in front of the RR tire. Still have the CAT
though.
Louder? Yeah, on the outside but not on the inside. Not enough to get
you in trouble.

Now to fuel the off-topic part...

A diesel engine, with no throttle plate, AND NO TURBO, will draw in the same
volume of air per each crankshaft revolution. Thats roughly 1.4 liters of air
per revolution. (Assuming 100% volumetric efficiency)
As RPMs increase, some "ramming" or "stacking" of air is possible in a
naturally aspirated engine, but its not enough to push beyond 100% V/E.
Adding a turbo or super charger can push V/E well beyond 100% because
you now have an additional "air pump" forcing air into the cylinders.
As the piston moves down, 700 cc's of air fills the cylinder, plus an additional
X cc's is packed (compressed) in there courtousy of the turbo charger.
The volume of air that fills the cylinder can vary depending on abient air temp,
compressed air temp, outside air pressure, impeller/tubine speed, and
impeller blade angle.

Threeweight · **Joined:** Mon May 14, 2007 5:57 pm **Posts:** 679

2mopar_diesels wrote:

I just asked simply about how a strait pipe sounds in the CRD Liberty and it went into the area of throttle/air intake & turbo restriction/fueling etc. all good info, just not what I was looking for. Thats all. I'm not at all new to diesel tech, just new to the Liberty CRD.

I ran mine with a cheap glass pack for a while (basically a straight pipe). I didn't like it. Had a nasty, headache inducing resonace between 45-55 mph, and it made it hard to really enjoy the radio/CD's on road trips. Replaced the glass pack with a Magnaflow, like it much better.

CRDMiller · **Posted:** Mon Sep 15, 2008 11:37 pm

Threeweight, your experiences are in line with mine, and I absolutely agree with the use of radio/cb, however I do wonder if an actual straight pipe would be less annoying.

My problem is that i am not satisfied with the loudness of the crd with the muffler (black super 44), but the open flange is defiantly too loud/annoying (at times, gutted part trap) I love it open when i'm around town but i absolutely hate it when i'm driving up wildcat canyon.

Stan Wright · **Posted:** Tue Sep 16, 2008 5:26 pm

2mopar_diesels wrote:

I just asked simply about how a strait pipe sounds in the CRD Liberty and it went into the area of throttle/air intake & turbo restriction/fueling etc. all good info, just not what I was looking for. Thats all. I'm not at all new to diesel tech, just new to the Liberty CRD.

Here is a recording I made of mine with a gutted cat, no muffler, and a side exit exhaust. It was recorded from the passenger seat with the window down.

http://liberty.eurekaboy.com/exhaust.wav

nursecosmo · **Posted:** Tue Sep 16, 2008 6:36 pm

Stan Wright wrote:

2mopar_diesels wrote:

I just asked simply about how a strait pipe sounds in the CRD Liberty and it went into the area of throttle/air intake & turbo restriction/fueling etc. all good info, just not what I was looking for. Thats all. I'm not at all new to diesel tech, just new to the Liberty CRD.

Here is a recording I made of mine with a gutted cat, no muffler, and a side exit exhaust. It was recorded from the passenger seat with the window down.

http://liberty.eurekaboy.com/exhaust.wav

Ooooh. I like that sound.

2mopar_diesels · **Posted:** Wed Sep 17, 2008 1:10 am

Oh heck yes!!! Thats a cool sound! That was with the full 3" exhaust rite?

CRDMiller · **Posted:** Wed Sep 17, 2008 10:34 am

Stan, That is exactly what mine sounds like with a turn down /open flange, and i'm guessing your ears bleed under load? Or phrased another way, when on the freeway, can you hear the bass of the stock stereo :P

Stan Wright · **Posted:** Wed Sep 17, 2008 9:03 pm

2mopar_diesels wrote:

Oh heck yes!!! Thats a cool sound! That was with the full 3" exhaust rite?

No, that's when I was still messing with the 2 1/2" exhaust.

Stan Wright · **Posted:** Wed Sep 17, 2008 9:15 pm

CRDMiller wrote:

Stan, That is exactly what mine sounds like with a turn down /open flange, and i'm guessing your ears bleed under load? Or phrased another way, when on the freeway, can you hear the bass of the stock stereo

None of the several exhaust configurations I've tried were loud (to me). Most of them weren't much louder than stock. The 2 1/2" straight pipe in the recording had more 'growl' than anything else. I'm guessing the gutted cat was still performing some muffling. The only configuration I found annoying was the 3" true straight pipe that exited the rear. It sounded like an old junker car and had some drone...and it also performed the best.

Side note: Stock stereo? It was gone the first day. :twisted:

bigugly · **Posted:** Sat Sep 20, 2008 11:53 pm

I got rid of my muffler on Friday. Muffler shop used 2" stainless since that was the inlet size on the muffler and then connected to the rest of the stock exhaust.

Has a nice low rumble but it is a little irritating a lower speeds. At highway speeds around 70-75 it is not bad. Not sure I like the additional noise. I might put a magnaflow on if I can't handle the additional noise. Regardless I am not doing anything until I run 5 or 6 tanks of diesel through the CRD without any muffler to see if there is any mileage improvement.

mackruss · **Posted:** Sat Sep 27, 2008 9:05 am

This is what i did.

Sorry, i'll resize the pics and repost.

ATXKJ · **Posted:** Sat Sep 27, 2008 9:15 am

Mack - you might want to resize the pictures '2048px × 1512px' really stretches the window

although good pictures

Strait Pipe or not to Strait Pipe???

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